The invention relates to a mechanical servomotor.
Servomotors of this type are often used in manually-operated spindles in vices and other devices requiring a high clamping pressure, and are disclosed in British Patent GB-A-614 904 and German Patent document DE-G-28 44 265. A sliding primary member having wedge faces is mounted inside a housing so that the wedge faces are next to roller bodies, there being a rolling action between their opposed peripheral side and fixed abutting faces. The present invention is concerned with the problem that despite this rolling action, servomotors of this type are actually sluggish in action and subject to much wear.
The investigations of the applicant have revealed that the rolling condition can be maintained only to a certain extent. At many points and in various movement phases there tends to be a sliding friction instead of the desired rolling friction. This phenomenon is inherent in the system of the known designs and cannot be corrected merely by altering relative sizes.
Attempts have been made to ensure a rolling friction, as evidenced in German Patent document DE-C-23 08 175, which discloses a toggle lever servomotor comprising two toggle-like roll bodies. This design requires that both roll bodies be secured at both ends to avoid a mutual displacement, as otherwise the faces of the one roll body would not roll exactly on the faces of the other roll body associated with it so that its resulting moving path would not be correct. However, the displacement of the support point toward both sides of each toggle-like roll body means that only small power amplifications can be expected. To avoid great frictional forces over long paths the stroke produced by the roll bodies will usually be quite small.